A model is proposed to describe the photoelectron decay process at room temperature in cubic AgCl microcrystals homogeneously doped with K4Fe(CN)6. By combining calculation of the kinetic equations resulted from the model with a microwave absorption dielectric-spectrum measuring technique, the capture cross-section and the trap depth of shallow electron traps induced by [Fe(CN)6]4- at room temperature are obtained, which are 3.560×10-17cm2 and 0.115eV, respectively. Based on the two parameters, the optimal doping amount of K4Fe(CN)6 is easily gained to be 2ppm by computer calculation.